Many scientists content that release of halogen refrigerants into the atmosphere deleteriously affects the ozone layer that surrounds and protects the earth from ultraviolet solar radiation. Recent international discussions and treaties, coupled with related regulations and legislation, have renewed interest in devices for recovery and storage of used refrigerants from refrigeration equipment for later purification and reuse or for proper disposal. U.S. Pat. No. 4,261,178, assigned to the assignee hereof, discloses a refrigerant recovery system in which the inlet of a compressor is coupled through an evaporator and through a manual valve to the refrigeration equipment from which refrigerant is to be recovered. The compressor outlet is connected through a condenser to a refrigerant storage container. The condenser and evaporator are combined in a single assembly through which cooling air is circulated by a fan. Content of the storage container is monitored by a scale on which the container is mounted for sensing weight of liquid refrigerant in the container, and by a pressure switch coupled to the fluid conduit between the condenser and the container for sensing vapor pressure within the storage container. A full-container condition sensed at the scale or a high-pressure condition sensed at the pressure switch terminates operation of the compressor motor. A vacuum switch is positioned between the inlet valve and the evaporator for sensing evacuation of refrigerant from the refrigeration system and automatically terminating operation of the compressor motor.
U.S. Pat. Nos. 4,768,347, 4,809,520 and 5,038,375, also assigned to the assignee hereof, disclose a refrigerant recovery system that includes a compressor having an inlet coupled through an evaporator and through a solenoid valve to the refrigeration equipment from which refrigerant is to be recovered, and an outlet coupled through a condenser to a refrigerant storage container or tank. The refrigerant storage container is carried by a scale having a limit switch coupled to control electronics to prevent or terminate further refrigerant recovery when the container is full. The scale comprises a platform pivotally mounted by a hinge pin to a wheel cart, which also carries the evaporator/condenser unit, compressor, control electronics, and associated valves and hoses.
Although the systems disclosed in the noted patents address and overcome problems theretofore extant in the art, further improvements remain desirable. For example, a problem remains relative to operation at elevated ambient temperature conditions. Problems have been encountered in connection with thermal overload at the compressor or termination of operation due to high pressure within the refrigerant storage container. Condensing capacity of the condenser could be increased, which would reduce compressor load but increase cost of the unit. Alternatively, compressor suction pressure could be decreased to decrease mass flow rate and condenser heat rejection requirements. However, efficient operation of the unit favors increased rather than decreased refrigerant mass flow rate.
It is therefore an object of the present invention to provide a refrigerant recovery system, and more specifically a refrigerant recovery and purification system of the described character, having enhanced capabilities for efficient and reliable operation at both normal and elevated ambient temperatures. A more specific object of the present invention is to provide a system of the described character that is economical to manufacture and reliable over an extended operating lifetime. A further object of the present invention is to provide a system of the described character that satisfies the foregoing objectives while being easy to operate.